Russian investigators were today hunting for the bomber behind Friday's train crash, in which 25 people died and nearly 100 were injured when their luxury express travelling from Moscow to St Petersburg was blown off the rails.

Russia's interior minister, Rashid Nurgaliev, said investigators were following several leads. They were attempting to trace a number of suspects spotted in the village near the site of the crash, including a stockily built man with red hair.

Nurgaliev said his officers were preparing to release a photo-fit of the man, aged about 40. But he cautioned: "This is preliminary information. We need to verify it." Sources said locals had noticed strangers in the sparsely populated rural district in the Tver region.

The Nevsky Express was carrying 682 passengers and 22 crew from Moscow to Russia's second city, St Petersburg. It was derailed at 9.34pm, close to the village of Uglovaka, 250 miles north-west of Moscow.

Another body was recovered from the wreckage this afternoon. Relatives were identifying the dead at a morgue in nearby Tver. Some 92 injured passengers were being treated in hospital and 12 people were unaccounted for, officials said.

Yesterday the head of Russia's FSB counter-terrorism agency, Alexander Bortnikov, said a powerful improvised bomb caused the derailment, sending the last three wagons on the 14-carriage train hurtling off the rails. Officers recovered "elements of an explosive device", containing the equivalent of 7kg (15.4lb) of TNT, he said.

The Kremlin has declined to say who it believes carried out the bombing amid speculation that the terror attack was the work of Chechen rebels. On Saturday a radical neo-Nazi group, Combat 18, also claimed responsibility. Other nationalist groups later denied the report.

The state-controlled TV channel Vesti hinted today that investigators were concentrating on a Chechen link. Vesti said they were looking at Pavel Kosolapov, an ex-soldier and former associate of the late Chechen rebel leader Shamil Basayev.

Russian prosecutors accused Kosolapov of carrying out a similar attack in 2007, also on the Nevsky Express between Moscow and St Petersburg, in which 19 people were injured. He remains on the run. Prosecutors arrested two residents of Ingushetia and charged them with helping to carry out the earlier derailment.

Alexei Malashenko, an expert on the north Caucasus at Moscow's Carnegie centre, said Friday's bombing could have been the work of Chechen rebels. He said: "I think [the rebels] want revenge. They want to create an Islamic space, even within the framework of Russia."Over the last two years the Islamists' insurgency in Russia's volatile north Caucasus has dramatically worsened, with the Muslim republics of Ingushetia, Chechnya, Dagestan and Kabardino-Balkaria in a state of near civil war.

Rebel fighters have carried out numerous attacks in recent months, including suicide bombings, in their apparent attempt to establish an Islamic caliphate.

The state-run railway company Russian Railways said train traffic was fully restored after repairs on the busy line between the capital and St Petersburg.

President Dmitry Medvedev called for calm , while the leader of the dominant Russian Orthodox church, Patriarch Kirill, urged Russians not to give in to fear, saying they should help authorities and "display firm will for a victory over terror".

"Our people have been challenged. A demonstrative crime of which any one of us could have been a victim has been committed. They want to frighten everybody who lives in Russia," he said.